There are in existence numerous devices for charging batteries including drycell batteries of the AA, C and D types wherein one or more batteries to be charged are positioned in the charging device which is connected to or plugged into a source of charging energy. Some batteries require a fairly long charging period, typically fourteen (14) hours or longer while other batteries have been developed including nickel-cadmium batteries which can be fast charged, sometimes in an hour or less. Those batteries that require the longer charging periods are generally of the same overall physical size and shape as batteries which can be fast charged but the fast charge batteries are usually distinguishable in some way such as by having narrower positive terminals or bushings. It is therefore incumbent on those building battery chargers capable of charging both types of batteries to provide means for distinguishing batteries which can be fast charged from those that can be charged only at a slower rate. The present invention teaches the construction of a battery charger having novel means for distinguishing batteries which can be fast charged from those which cannot, and for controlling the battery charger so that the charger will charge a battery positioned therein at the required charging rate depending upon the type of battery that it is. The present charger may also include means to control whether certain batteries can receive a charge.
The closest known prior art to the present construction is disclosed in U.S. Pat. Nos. 3,391,321 (Otu), 3,579,075 (Floyd), 4,403,182 (Yek), 4,577,144 (Hodgman et al), 4,645,996 (Toops), and 4,816,735 (Cook et al).
In order to physically distinguish between batteries that can be fast charged from those that cannot, the fast charge batteries of the type chargable in the present charger are constructed to have their positive terminals or bushings which protrude from the center of one end of the battery of a different, preferably smaller, diameter than the diameter of the positive terminals on batteries which cannot be fast charged. The smaller diameter positive terminals on the fast charge batteries are used in the present battery charger to actuate switch means such as microswitch means to establish a circuit condition in the charging circuit which enables any such battery to be charged at the faster rate. Those batteries which cannot be fast charged, which have the larger diameter positive terminals, will not be able to actuate the switch means and therefore the charger circuit will only be able to charge these batteries at a more conventional slower charging rate. Since the conventional batteries need to be charged at a slower rate than the faster rate they will not be damaged by having the slow charging rate applied to them. On the other hand those batteries which are capable of being fast charged will be able to actuate associated switch means to establish the circuits or circuit conditions necessary to fast charge them. This distinction will be made automatically when the batteries are installed in the battery charger. The present invention therefore is directed to providing means on a battery charger for distinguishing batteries that can be fast charged from batteries that cannot be fast charged, and the means for doing so establish circuit conditions which will produce the desired charging rate for each battery installed so that both fast and slow charge batteries can be charged simultaneously but at different rates as required for each.
The present battery charger may have means for accommodating a plurality of batteries to be charged simultaneously and the size or diameter of the positive battery terminals, as aforesaid, will be used to control the charging rate for certain batteries positioned in the charger.
The present battery charger has a compartment with positions for installing a plurality of batteries including the possibility of installing batteries of different sizes as well as different charging rates to be charged. For example, the same compartment can accommodate AA, C, and D batteries in each position. In the case of the AA batteries the charger may also have optional special provision for checking a battery voltage or a battery continuity of each such battery to see if it is even capable of being charged. If a certain battery voltage is within a predetermined voltage range such as greater than zero volts, it indicates that battery can be charged and the circuits for doing so will be established. If not, the circuit is controlled to prevent charging. It is expected however that all batteries will receive a charge for a short period of time such as for a few cycles before a determination is made as to whether the battery voltage is such that the battery can be charged or not.
The closest known prior art to the idea of measuring a battery voltage (or battery continuity) using an electrical contact to make contact to an intermediate location on the battery housing are disclosed in U.S. Pat. Nos. 3,506,902 (Sullivan) and 4,628,243 (Hodgeman et al) and in pending U.S. Pat. application Ser. No. 377,370, filed July 7, 1989 and assigned to Applicant's assignee.
No known battery charger is capable of accommodating and charging a plurality of the same or of different size batteries some or all of which are capable of being fast or slow charged and to do so simultaneously and individually depending upon the types of batteries involved. The closest known prior art to a device having such features in combination is disclosed in Johnson et al U.S. Pat. Application Ser. No. 248,962, filed Sept. 26, 1988 and assigned to Applicant's assignee. The prior art construction is able to charge a plurality of batteries simultaneously but it has no means for distinguishing between those batteries that can be fast charged from those that must be slow charged, and simultaneously charging all such batteries at their own respective charging rates and has no means for determining that certain batteries of one type are capable or not of being charged based on a battery voltage or continuity measured from a contact at an intermediate location on the battery.